Melt semi-sweet chocolate chips in a microwave-safe bowl at 30-second intervals until smooth.
Using an electric mixer, beat butter and brown sugar for about 5 minutes.
Beat in the eggs, one at a time, beating just until incorporated.
Add melted chocolate and beat just until mixed in.
Whisk together flour, baking soda, and salt.
Add flour mixture to chocolate mixture, alternating with sour cream, beginning and ending with flour.
With mixer on low, gradually add hot water. Add vanilla.
Pour batter into a 10×14-inch pan that has been lined with aluminum foil and sprayed with cooking spray.
Bake at 350 degrees for 40 minutes, or until a toothpick inserted in the middle comes out clean.
To make icing, bring brown sugar, whipping cream, and butter to a boil in a medium saucepan, stirring frequently. Boil for 1 minute.
Remove from heat and whisk in powdered sugar and vanilla. Stir in pecans.
Let mixture cool for about 3 to 5 minutes and then pour on top of cake.
Let cool completely and then cut into squares.
